The Royals and Chen had agreed to terms on a one-year contract with a mutual 2015 option in February.

The itinerant 37-year-old Chen found a home with the Royals, for whom he has played since 2009. This season, the oldest pitcher on the Kansas City staff struggled to a 2-4 record and 7.45 earned run average over 13 appearances -- seven of those as a starter.

Chen has a career mark of 82-80 with a 4.58 ERA in 398 games -- 225 as a starter -- over 15 seasons with the Braves, Phillies, Mets, Expos, Reds, Astros, Red Sox, Orioles, Rangers and Royals.

To fill the roster slot, the Royals recalled pitcher Louis Coleman from Triple-A Omaha. Coleman last appeared in the majors just prior to the All-Star break, going 1-0 with a 7.48 ERA in 20 appearances total in 2014.